The invention relates to a sealing system for drive units consisting of motors, in particular fast-running motors, with a directly flanged-on gear unit, in particular for passenger conveyor systems, such as escalators and moving walkways.
German reference 42 42 762 discloses a gear unit, used in particular for the drive units of escalators, moving walkways or the like. The input shaft and/or the output shaft of this gear unit rests on tapered roller bearings and is sealed axially toward the outside by at least one shaft seal, wherein a lubricating oil circulating element is provided axially between the tapered roller bearing and the shaft seal. Owing to the design, however, the tapered roller bearing pumps out the lubricating oil. The lubricating oil-circulating element is a component that holds the tapered roller bearing (s), wherein the component is an adjustment screw provided with centrifugal elements. The shaft seal consists of several chambers that can be axially pre-tensioned between the sealing elements that form. It was the object of the aforementioned reference to eliminate almost completely the leakage in the shaft of a gear-unit, in particular a worm gear unit, thus increasing the operating time, and to securely avoid damage to the sealing lip or sealing lips of the shaft seal, even if there is a lack of lubrication. Worm gears as a rule represent slow-moving gear unit elements, so that it may be difficult in some circumstances to supply the respective sealing lip with lubricating oil, so as to prevent it from failing prematurely.
German reference C 32 38 780 discloses a lubricating oil system for gear units, comprising at least one oil-collecting pocket and an annular collecting groove, open toward the peripheral surface of a rotating gear unit shaft, for lubricating oil pumped by a pump that is arranged on the gear unit shaft. Radial channels are assigned to the pump for this and the pump intake location is connected to the oil-collecting pocket, wherein at least one channel extends from the annular collecting groove toward the inside of the gear unit shaft and to at least one lubricating point arranged on the inside of the gear unit shaft. The pump is designed as centrifugal pump and comprises an essentially disk-shaped impeller provided with vanes. The radial channels are designed as radially inward extending reversing channels, installed permanently on the housing, which extend from a hydraulic oil collecting chamber arranged radially on the outside of the centrifugal pump toward the inside and are connected to the annular collection groove.
The German magazine Konstruktion 39 (1987), 3rd Issue, pages 107-113 shows non-contacting shaft seals for liquid-splattered sealing locations. This reference provides a general design overview for non-contacting sealing systems in use. It also provides clues for configuring the ambient installation area for the sealing system, the sealing element itself as well as the re-circulation of the liquid. In addition, reference is made to problems concerning the undesirable inflow of dust into the chamber to be sealed off, which have not yet been solved.
It is the object of the present invention to improve a sealing system with simple design for drive units, consisting of motors with directly flanged-on gear units, in particular fast-running motors, in such a way that on the one hand a leakage during the transport (tilting) and installation of the passenger conveying system is securely avoided and, on the other hand, the lubricating oil is securely prevented from flowing out of the gear unit in the direction of the motor, even during a later seal failure in the operating condition.
This object is achieved with a sealing system for drive units consisting of motors, particularly fast running motors with a directly flanged-on gear unit, used especially for passenger conveyor systems such as escalators and moving walkways. The sealing system comprises at least one sealing element designed as radial shaft seal, at least one centrifugal element as well as at least one cover and suctioning element, which is arranged on the gear unit side in front of the sealing element. A lubricating oil collecting chamber provided in the region for the centrifugal element is connected via at least one channel extending in the direction of the cover and suctioning element to the gear unit chamber located on the intake side of the cover and suctioning element, approximately above the oil level.
Advantageous modifications of the subject matter of the invention follow from the dependent claims.
On the one hand, the subject matter of the invention allows the movement of the passenger conveyor system, such as an escalator or a moving walkway, independent of the respective angles of inclination. On the other hand and owing to the system for re-circulating the lubricating oil, it makes it possible to safely prevent lubricating oil from flowing out of the gear unit in the direction of the motor during operations, even in case of failure of the sealing element that operates contacting, at least once it is installed.
During the fully mounted state of the passenger conveyor system, the oil level inside the gear unit chamber can be lowered to a level below the largest peripheral extension of the cover and suctioning element thus making it possible to save several liters of lubricating oil for each gear unit. As a result of its spatial arrangement as well as the outer peripheral surface that is tapered in the direction of the sealing element, the cover and suctioning element on the one hand prevents that lubricating oil (centrifugal oil) outside of the oil level is constantly pumped with more or less high pressure in the direction of the sealing element. On the other hand, it ensures that the lubricating oil, which has actually penetrated the sealing element, is once more suctioned in via the centrifugal disk in the direction of the lubricating oil collection chamber and via the channel in the direction of the gear unit chamber. In both cases, the centrifugal force of the cover and suctioning element is utilized on location for the respective purpose.
The subject matter of the invention thus creates a lubricating oil circulation system that is effective even if the sealing element has failed during operations and in any case securely prevents lubricating oil from leaving the gear unit in the direction of the directly flanged-on motor. The sealing system, which is preferably designed as installation unit, is a one-piece structural component, consisting of the cover and suctioning element and the centrifugal element, wherein the radial shaft seal, which may be designed with several lips if necessary, is mounted on a radially offset leg of the centrifugal element.
As a result of the circulation system for the possibly escaping lubricating oil, designed in this way, the sealing element is actually unnecessary during the operating state. The element therefore actually serves only a transport and installation purpose and is operatively connected to a transport safety device that may exist, which ensures an effective separation of the lubricating oil collection chamber from the channel extending in the direction of the gear unit chamber.
The seal location between an especially fast-running motor and a gear unit filled with synthetic oil must be considered a problem for the following reasons:
Synthetic oil is not compatible with all types of sealing lip material. Also, not all sealing-lip materials are resistant to high temperatures, such as occur in particular with fast-running motor output shafts.
During the step or tread pad installation and replacement, a temperature of more than 100 degrees Celsius is easily reached during the inching mode, considering the fact that the motor runs up during the short period, but that the associated ventilator cannot produce the necessary cooling output. Thus, a sealing lip material on the basis of Viton(copyright)1 offers itself for this. Over the long run, this high-temperature resistant sealing lip material, however, is not resistant to synthetic oil, so that one of the parameters is taken into account, but not the other one.
1 Note: registered trademark for series of fluoroelastomers (see attached page) 
With respect to their service life, radial shaft sealing rings on NBR2 basis are mostly resistant against synthetic oil, but will fail after relatively short service life periods at the aforementioned high temperatures.
2 Note: NBR=nitrile-butadiene rubber (see attached pages) 
Thus, the shaft-sealing ring, which can easily be omitted during the operating state since the re-circulation of the lubricating oil to the gear unit chamber is ensured by the other sealing system components, therefore can be produced as cheap NBR component. Thus the sealing system can be produced very cheaply in this problematic area and can be installed as one unit. A possible retrofitting with the sealing system designed as installation unit is also conceivable.